Considering how many things are a portion of our body and simultaneously considered separate living organisms it's pretty bizarre to have such an explicitly defined view of consciousness in our existence that can let you point at a cat or human and say "That is a conscious being".
We know what that means to us but we can only assume others have similar experiences.
And the only way to do that is by looking at behaviours.
So we point at cats and humans and say they're conscious because they demonstrate behaviours that we associate with our subjective experience of consciousness - goal seeking and planning, apparent emotional responses, awareness of context, decision making, pattern- and repetition-based learning, and other kinds of responsiveness and agency.
It's a very specific idea of what consciousness is, and it only really applies at human scale.
If an object/entity/subsystem experienced qualia of any kind - including the experience of any kind of self-object, from the most rudimentary to the most universal - without demonstrating any of the behaviours at a human scale, we'd never know.
some argue (using data and experimentation) that trees and/or other plants express all of these behaviors
I think the common conceptualization of consciousness is the only definition that is useful, or makes sense. Which is something that can experience things. For many reasons, I don't think these rudimentary behaviors in plants suggest they are capable of experience.
But also jellyfish has goal seeking behavior, and a most of those other characteristics you mention, and my intuition (based on the vastly different neural structure and anatomy), is that they experience probably nothing.
I know I see the color red in a particular way. I have a consciousness experience of seeing red things that _feels like_ something. I can talk about wavelengths, or put color into a theory, but none of this explains the feeling of seeing the color red.
How do I know if someone else has the same subjective experience as me regarding color, or taste, or thought form? I don't, it can't be known.
This "it can't be known" (unfeasibility of proving or disproving anything about this phenomenon) is enough for most science-like minds to discard all of this as nonsense. For these, there is no phenomenon, this subjective experience arises from emerging properties.
The emerging properties model is not unfeasible, we could test it, if we were able to observe these properties emerging. However, we didn't, it's hard. Although feasible, it has not been proven or disproven, and modeling the brain has been a challenge.
So, for now, the only thing you can point and say "that is a conscious being" with abolsute confidence is yourself. Only you know that, and you can't share that proof. This notion was popularized as the philosophical zombies thought experiment.
Maybe it is a tool trying to optimize food acquisition. That's not a completely unreasonable idea. But how would you go about testing that hypothesis? How can you know that some abstract process is working when you can't even prove to others it exists?
One thing you can do is disrupt the smaller individual components that make up the emergent property, and see if the property continues to exist.
I.e. you can put a motorized egg beater in your brain, and see if you still have the emergent properties of consciousness. My prediction is that the property will suddenly disappear.
Or can cut off blood to the brain for a little while.
The counter-argument will be that the consciousness unrecognizably changes, and once the blood comes back, that configuration of matter generally restores. None of this is convincing to me in any way, and I genuinely desperately want someone (a panpsychist) to explain how I'm thinking about this incorrectly.
I'm not implying consciousness is some mythical undiscovered force. My point is: How would you know if the components that you are toying with are indeed relevant to consciousness and not some proxy or supporting structure?
The answer is: you can't know. You can reach lesser conclusions (under the effect of drug X, area Y of the brain has decreased activity, resulting in change of behavior Z), but it says nothing about that subjective experience I mentioned earlier (qualia).
I don't doubt we could brute force this into a meaningful discovery, carefully mapping each part of the brain until we figure it out completely, including qualia. We're not there yet though.
If interested, the reason I don't like the radio analogy is that it presupposes that the configuration of the brain, and inputs isn't fundamentally the constituents of consciousness.
On the flip side, to fix the analogy: if I cut off the antenna of a radio, I would argue it ceases to become a radio by any reasonable definition (assuming we're talking about a device that receives radio waves and plays them back in the form of sound). You just have something that's very close to a radio. It has nothing to do with whether radio waves exist or don't.
As long as you agree that it's conceivable that there's experimentation (brute force or otherwise), then I think we're on the same page.
I think the onus is on the brain folks. In order to solve this, they need to prove that qualia lives as an emergent property in the brain. I'm not presuposing tht the consciousness lives somewhere outside the brain, I'm asking for proof that it does (which is reasonable).
What we have is proof of neither and no way to get there. The reductionist approach offers a more systematic way of approaching the problem, but there are no guarantees. Breaking down a problem into smaller questions is not a proof if there are still smaller questions unanswered.